Heat transfer tube with multiple enhancements

ABSTRACT

A heat transfer tube including an inner surface including a plurality of grooves. The plurality of grooves includes at least primary grooves and secondary grooves, wherein the primary grooves extend axially along a length of the tube, and the secondary grooves intersect the primary grooves.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S.application Ser. No. 14/874,708 filed Oct. 5, 2015, which claims thebenefit of U.S. Provisional Application No. 62/060,051, filed on Oct. 6,2014. The entire disclosures of each of the above applications areincorporated herein by reference.

FIELD

The present disclosure relates to a heat transfer tube including axialand non-axial grooves therein.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Copper tubing is generally used for condenser tubing in, for example, anair conditioner, refrigerator, or heat pump. While copper providesexcellent heat transfer, copper is an expensive material. Thus,materials such as aluminum are now being used to form condenser tubing.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

The present disclosure provides a heat transfer tube. The heat transfertube includes an inner surface including a plurality of grooves. Theplurality of grooves includes at least primary grooves and secondarygrooves, wherein the primary grooves extend along a length of the tube,and the secondary grooves intersect the primary grooves.

The heat transfer tube may include secondary grooves that are helicallyformed.

The heat transfer tube may also include tertiary grooves that intersectat least the primary grooves.

The tertiary grooves may intersect the secondary grooves.

The tertiary grooves may be helically formed.

The heat transfer tube may include aluminum.

The present disclosure also provides a method of forming a heat transfertube. The method includes extruding a tube including a plurality ofaxial primary grooves on an inner surface thereof; and forming aplurality of secondary grooves on the inner surface using a firstforming tool, wherein the secondary grooves intersect the primarygrooves. In the forming process, the ridges between the primary groovesmay be deformed to partially or completely block the primary grooves.

The first forming tool may include a plurality of threads at a firstpitch and a first height. Alternatively, the first forming tool mayinclude expanding tools or cams that press the secondary grooves intothe tube

The first forming tool may form the secondary grooves in a helicalorientation that may be either continuous or discontinuous, formingdiscrete rings or other paths.

According to the method, a plurality of tertiary grooves may also beformed on the inner surface using a second forming tool.

The tertiary grooves may intersect the primary grooves.

The tertiary grooves may intersect the secondary grooves.

The second forming tool may include a plurality of threads at a secondpitch and a second height and/or a different shape than the firstforming tool.

The secondary grooves and the tertiary grooves may each be helicallyformed.

The method may also include a step of cutting a length of tube from theextruded tube.

The length of tube may be cut from the extruded tube before forming thesecondary grooves.

Alternatively, the length of tube may be cut from the extruded tubeafter forming the secondary grooves.

The method may also include bending the heat transfer tube into ahairpin tube.

According to the method, the heat transfer tube may include aluminum.

The present disclosure also provides heat transfer tube having an innersurface including a plurality of grooves, wherein the plurality ofgrooves including at least primary grooves and secondary grooves. Theprimary grooves each extend helically in an axial direction along anddefined by a length of the tube and are open in a radial directiontoward a center of the tube. Adjacent primary grooves are separated by aridge. The secondary grooves intersect the primary grooves, and atlocations where the secondary grooves intersect the primary grooves,each of the primary grooves are entirely blocked in the axial directionof the tube without being blocked in the radial direction by a materialof the ridge that separates the adjacent primary grooves that isdeformed into one of the adjacent primary grooves.

The secondary grooves may be helically formed.

The inner surface may also include tertiary grooves that intersect atleast the primary grooves. The tertiary grooves may also intersect thesecondary grooves. The tertiary grooves may be helically formed.

The heat transfer tube may include aluminum.

At the locations where the secondary grooves intersect the primarygrooves, each of the deformations of the ridges that separate adjacentprimary grooves may be oriented in a same direction.

A depth of the secondary grooves may be greater than a depth of theprimary grooves.

The material of the ridge that is deformed into one of the adjacentprimary grooves restricts flow through the one primary groove.

The present disclosure also provides heat transfer tube having an innersurface including a plurality of grooves, wherein the plurality ofgrooves including at least primary grooves and secondary grooves. Theprimary grooves each extend helically in an axial direction along anddefined by a length of the tube and are open in a radial directiontoward a center of the tube. Adjacent primary grooves being separated bya ridge. The secondary grooves intersect the primary grooves, and atlocations where the secondary grooves intersect the primary grooves,each of the primary grooves are at least partially blocked in the axialdirection of the tube without being blocked in the radial direction by amaterial of the ridge that separates adjacent primary grooves that isdeformed into one of the adjacent primary grooves.

A depth of the secondary grooves may be greater than a depth of theprimary grooves.

Each of the primary grooves may be entirely blocked in the axialdirection of the tube without being blocked in the radial direction bythe deformation of the ridge that separates the adjacent primarygrooves.

The material of the ridge that is deformed into one of the adjacentprimary grooves restricts flow through the one primary groove.

The present disclosure also provides a heat transfer tube having aninner surface including a plurality of grooves, wherein the plurality ofgrooves including at least primary grooves and secondary grooves. Theprimary grooves each extend helically in an axial direction along alength of the tube and are open in a radial direction toward a center ofthe tube. The secondary grooves intersect the primary grooves. Atlocations where the secondary grooves intersect the primary grooves,each of the primary grooves are at least partially blocked in the axialdirection of the tube without being blocked in the radial direction by adeformation of a ridge that separates adjacent primary grooves, and adepth of the secondary grooves is greater than a depth of the primarygrooves.

Each of the primary grooves may be entirely blocked in the axialdirection of the tube without being blocked in the radial direction bythe deformation of the ridge that separates the adjacent primarygrooves.

At the locations where the secondary grooves intersect the primarygrooves, each of the deformations of the ridges that separate adjacentprimary grooves are oriented in a same direction.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a cross-sectional view of an exemplary heat transfer tubeaccording to a principle of the present disclosure;

FIG. 2 is a perspective view of a section of an exemplary heat transfertube according to a principle of the present disclosure;

FIG. 3 is a perspective view of a forming tool used to form grooves in aheat transfer tube according to a principle of the present disclosure;

FIG. 4 is a perspective view of a section of another exemplary heattransfer tube according to a principle of the present disclosure;

FIG. 5 is a micrograph of a section of an exemplary heat transfer tubeaccording to a principle of the present disclosure, wherein in theprocess of forming the secondary grooves, the primary grooves aresubstantially blocked by material deformed from the ridges betweenprimary grooves;

FIG. 6 is a micrograph of a section of an exemplary heat transfer tubeaccording to a principle of the present disclosure, wherein in theprocess of forming the secondary grooves, the ridges between primarygrooves are deformed to protrude into the primary groove withoutsubstantially blocking the groove;

FIG. 7 is a graph illustrating heat transfer results from a 7 mm tubeutilizing refrigerant 410 a, wherein the secondary grooves have adifferent depth in comparison to the primary grooves, where the percentdepth pertains to the percent the secondary groove cuts into the ridgebetween the primary grooves (e.g. at 30%, the secondary groove cutsthrough the top 30% of the ridge, and at 100%, the secondary groove cutscompletely through the ridge with both primary and secondary grooveshaving the same depth);

FIG. 8 is a graph illustrating heat transfer results from a 7 mm tubeutilizing refrigerant 410 a, wherein a tube including primary grooves iscompared to a tube including primary grooves and secondary grooves, andcompared to a tube including primary grooves, secondary grooves, andtertiary grooves;

FIG. 9 is a graph illustrating heat transfer results from a 7 mm tubeutilizing refrigerant 410 a, wherein a tube including primary grooves iscompared to the tube illustrated in FIG. 5, and compared to the tubeillustrated in FIG. 6; and

FIGS. 10 and 11 are perspective views of sections of additionalexemplary heat transfer tubes according to a principle of the presentdisclosure.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

FIG. 1 illustrates a tube 10 including a plurality of primary grooves 12separated by ridges 13. Tube 10 is generally cylindrically shaped andincludes an outer surface 14 that defines an outer diameter OD, and aninner surface 16 defining an inner diameter ID. Tube 10 may be formedfrom materials such as copper, aluminum, stainless steel, or any othermaterial known to one skilled in the art. Preferably, tube 10 is usedfor carrying a refrigerant in an air conditioner condenser, anevaporator, or heat pump.

Tube 10 may be extruded to include primary grooves 12. Primary grooves12, as illustrated, are axial grooves 12 that assist in increasing theinner surface area of tube 10. It should be understood, however, thatprimary grooves 12 can be helically formed without departing from thescope of the present disclosure (FIGS. 10 and 11). By increasing theinner surface area of tube 10, a greater amount of heat transfer canoccur between the refrigerant carried by tube 10 and tube 10. The numberand size of grooves 12 can be variable. As illustrated in FIG. 1, tube10 includes fifty-eight primary grooves 12. Tube 10, however, caninclude a greater or less number of primary grooves 12 without departingfrom the scope of the present disclosure. Further, although primarygrooves 12 are illustrated as including a rounded bottom 18, it shouldbe understood that primary grooves 12 can be square-shaped, oval-shaped,or V-shaped without departing from the scope of the present disclosure.Tube 10 has a thickness T in the range of about a third of an inch. Tube10, however, can have a greater or lesser thickness as desired.

To further increase the heat transfer capability of tube 10, tube 10 canbe further processed to include secondary grooves 20. As illustrated inFIGS. 2 and 10, secondary grooves 20 are non-axially formed so as tointersect primary grooves 12. The use of secondary grooves 20 along withprimary grooves 12 creates a complex inner surface 16 that maximizesheat transfer between the refrigerant carried by tube 10 and tube 10.Secondary grooves 20 may be formed orthogonal to primary grooves 12, orsecondary grooves 20 can be helically formed to intersect primarygrooves 12. The secondary grooves 20 may be continuously formed ordiscontinuously formed down the length of the tube 10. The secondarygrooves 20 may displace material from the ridges between the primarygrooves to form ridges on either or both sides of the secondary groovesthat may be continuous or discontinuous in nature to block or restrictthe flow fluid in the primary grooves.

FIG. 3 illustrates a forming tool 22 that may be used to form secondarygrooves 20. Forming tool 22 includes a proximal portion 24 that isdriven by a rotating tool (not shown), and forming tool 22 includes adistal portion 26. Distal portion 26 of forming tool 22 also includes athreading 28 that, as forming tool 22 is rotated, will form secondarygrooves 20 in tube 10. A pitch or spacing S between threads 30 can bemodified, as desired. Further, a height H of threads 30 can be adjusted,as desired. In this regard, height H of threads 30 can be formed greaterthan, equal to, or less a depth D of primary grooves 12 such thatsecondary grooves 20 have a different depth (e.g., greater or lesser) incomparison to a depth of primary grooves 12. Differing the depth ofsecondary grooves 20 can affect heat exchange between the refrigerantand the tube 10. As best shown in FIG. 7, when secondary grooves 20 havea depth that is 30% of the depth of the primary grooves 12, heattransfer is increased. FIG. 7 also shows that secondary grooves 20 thathave a depth this 50% or 100% of the depth of the primary grooves 12also increases heat exchange between the refrigerant and the tube 10.

In addition, an angle α at which threads 30 are arranged relative to anaxis A of forming tool 22 can be adjusted as desired. Regardless, itshould be understood that each of the spacing S, height H, and angle αcan be selected and adjusted based on the inner diameter ID of tube 10,and the desired flow rate of the refrigerant in tube 10. It should alsobe understood that the secondary grooves 20 may also be formed with avariety of tools that can be placed in the tube to deform the primarygrooves, resulting in secondary grooves 20.

Now referring to FIGS. 4 and 11, it can be seen that tube 10 may includeprimary grooves 12, secondary grooves 20, and tertiary grooves 32.Similar to secondary grooves 20, tertiary grooves 32 are non-axiallyformed so as to intersect primary grooves 12. Tertiary grooves 32 mayalso intersect secondary grooves 20. The use of tertiary grooves 32along with primary grooves 12 and secondary grooves 20 creates a complexinner surface 16 that maximizes heat transfer between the refrigerantcarried by tube 10 and tube 10. Tertiary grooves 32 may be formedorthogonal to primary grooves 12, or tertiary grooves 32 can behelically formed to intersect primary grooves 12. Further, tertiarygrooves 32 may be formed with a forming tool 22 similar to that used toform secondary grooves 20, with the spacing S, height H, and angle αbeing differed. The tertiary grooves 32 may have a completely differentshape or follow an entirely different path than the primary grooves 12and secondary grooves 20, and may be continuously formed ordiscontinuously formed.

Now referring to FIGS. 5 and 6, it can be seen that primary grooves 12(which travel from left to right in FIGS. 5 and 6) may be entirelyblocked (FIG. 5) or partially blocked (FIG. 6) by formation of thesecondary grooves 20 and/or the tertiary grooves 32. In this regard,tool 22 used to form second grooves 20 and/or tertiary grooves 32 candeform ridges 13 between primary grooves 12 during formation of thesecondary grooves 20 and/or the tertiary grooves 32 such that portionsof ridges 13 are deformed or forced into primary grooves 12. By forcingthe ridges 13 into primary grooves 12, heat transfer between therefrigerant and the tube 10 is increased due to restriction of the flowin primary grooves 12, which increases turbulence in the flow of therefrigerant in tube 10. This heat transfer effect is most pronouncedwhen the ridges 13 between the primary groves 12 are deformed tocompletely block or restrict the flow in the primary groove 12. Itshould be understood, however, that partial blockage of primary groove12 by deformed portions also achieves an increase in heat transferbetween tube 10 and the refrigerant (FIG. 9).

As shown in FIG. 8, the use of secondary grooves 20 and/or tertiarygrooves 32 assists in improving the heat transfer characteristics oftube 10 as much as 30% in comparison to a tube 10 including only axialprimary grooves or only helical primary grooves. In this regard, in aconventional tube including only axial primary grooves or only helicalprimary grooves, the refrigerant flow tends to settle into and followthe grooves, which forms a refrigerant boundary layer within the tubethat resists and/or restricts heat transfer between the refrigerant andthe tube. The use of secondary grooves 20 and/or tertiary grooves 32disrupts the flow of the refrigerant through primary grooves 12 toprevent formation of a refrigerant boundary layer. In this regard, theflow of the refrigerant is disrupted by the intersection of the primarygrooves 12 by each of the secondary grooves 20 and/or the tertiarygrooves 32, which causes the refrigerant flow to break off from primarygrooves 20 and also creates turbulence in the refrigerant flow thatenhances heat transfer.

To form tube 10, a length of tube (e.g., 500 feet) is extruded toinclude primary grooves 12 that are either axial or helical. A desiredlength of tube 10 is selected, and the desired length is cut from thelength of tube. A secondary process is then conducted to form secondarygrooves 20 and/or tertiary grooves 32. Specifically, a forming tool 22is selected having the desired spacing S, height H, and angle α ofthreads 30. Forming tool 22 is inserted into tube 10 and rotated to formsecondary grooves 20 and/or tertiary grooves 32. A single pass ofmultiple forming tools 22, or multiple passes of multiple forming tools22 can be done to form secondary and/or tertiary grooves 20 and 32.Thus, it should be understood that tube 10 can also include any numberof grooves (not shown), etc.

After forming at least the secondary grooves 20, the tube 10 may then bebent into a desired configuration (e.g., a hairpin). Alternatively, tube10 may be bent into the desired configuration prior to forming secondaryand/or tertiary grooves 20 and 32. In addition, it should be understoodthat the second processing can occur before or after tube 10 is cut fromthe length of tube, and before or after lubricant is applied to tube 10that is used during expansion of tube 10.

Alternatively, the secondary grooves 20 may formed in a continuousfashion (e.g. drawing) before cutting the tube 10 to final length. Theforming tool may be designed in a way that the tool is self-rotating inthe continuous process, simplifying the process. The continuous processmay be performed in conjunction with other existing processes, such asextrusion or cutting, or performed as a standalone coil to coiloperation.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A heat transfer tube, comprising an inner surfaceincluding a plurality of grooves, the plurality of grooves including atleast primary grooves and secondary grooves, wherein the primary grooveseach extend helically in an axial direction along and defined by alength of the tube and are open in a radial direction toward a center ofthe tube, adjacent primary grooves being separated by a ridge, thesecondary grooves intersect the primary grooves, and at locations wherethe secondary grooves intersect the primary grooves, each of the primarygrooves are entirely blocked in the axial direction of the tube withoutbeing blocked in the radial direction by a material of the ridge thatseparates the adjacent primary grooves that is deformed into one of theadjacent primary grooves.
 2. The heat transfer tube of claim 1, whereinthe secondary grooves are helically formed.
 3. The heat transfer tube ofclaim 1, further comprising tertiary grooves that intersect at least theprimary grooves.
 4. The heat transfer tube of claim 3, wherein thetertiary grooves intersect the secondary grooves.
 5. The heat transfertube of claim 4, wherein the tertiary grooves are helically formed. 6.The heat transfer tube according to claim 1, wherein the heat transfertube includes aluminum.
 7. The heat transfer tube according to claim 1,wherein at the locations where the secondary grooves intersect theprimary grooves, each of the deformations of the ridges that separateadjacent primary grooves are oriented in a same direction.
 8. The heattransfer tube according to claim 1, wherein a depth of the secondarygrooves is greater than a depth of the primary grooves.
 9. The heattransfer tube according to claim 1, wherein the material of the ridgethat is deformed into one of the adjacent primary grooves restricts flowthrough the one primary groove.
 10. A heat transfer tube, comprising aninner surface including a plurality of grooves, the plurality of groovesincluding at least primary grooves and secondary grooves, wherein theprimary grooves each extend helically in an axial direction along anddefined by a length of the tube and are open in a radial directiontoward a center of the tube, adjacent primary grooves being separated bya ridge, the secondary grooves intersect the primary grooves, and atlocations where the secondary grooves intersect the primary grooves,each of the primary grooves are at least partially blocked in the axialdirection of the tube without being blocked in the radial direction by amaterial of the ridge that separates adjacent primary grooves that isdeformed into one of the adjacent primary grooves.
 11. The heat transfertube according to claim 10, wherein a depth of the secondary grooves isgreater than a depth of the primary grooves.
 12. The heat transfer tubeaccording to claim 10, wherein each of the primary grooves are entirelyblocked in the axial direction of the tube without being blocked in theradial direction by the deformation of the ridge that separates theadjacent primary grooves.
 13. The heat transfer tube according to claim10, wherein the material of the ridge that is deformed into one of theadjacent primary grooves restricts flow through the one primary groove.14. A heat transfer tube, comprising an inner surface including aplurality of grooves, the plurality of grooves including at leastprimary grooves and secondary grooves, wherein the primary grooves eachextend helically in an axial direction along a length of the tube andare open in a radial direction toward a center of the tube, thesecondary grooves intersect the primary grooves, at locations where thesecondary grooves intersect the primary grooves, each of the primarygrooves are at least partially blocked in the axial direction of thetube without being blocked in the radial direction by a deformation of aridge that separates adjacent primary grooves, and a depth of thesecondary grooves is greater than a depth of the primary grooves. 15.The heat transfer tube according to claim 14, wherein each of theprimary grooves are entirely blocked in the axial direction of the tubewithout being blocked in the radial direction by the deformation of theridge that separates the adjacent primary grooves.
 16. The heat transfertube according to claim 14, wherein at the locations where the secondarygrooves intersect the primary grooves, each of the deformations of theridges that separate adjacent primary grooves are oriented in a samedirection.